Psoriasis is a chronic, immune-mediated, inflammatory skin disease, with a global incidence of approximately 2%, associated with significant morbidity and can have a substantial psychosocial impact on quality of life and well-being of patients. Plaque psoriasis is the most common form and affects approximately 80-90% of patients, manifesting as raised plaques on the skin; the disease usually begins in late adolescence and early adulthood and may persist through adult life. The extent of the affected body surface area (BSA) and the degree of skin manifestations, including erythema, induration, and scaling, defines the severity of psoriasis with approximately 20-30% of patients having moderate-to-severe disease.
Psoriasis is a multifactorial disease, of unknown aetiology, with autoimmune and autoinflammatory components. Multiple genome-wide association studies have linked variants in the genes for the IL-23 receptor to psoriasis susceptibility. Human IL-23 is primarily produced by antigen presenting cells and induces differentiation of T helper 17 (Th17) cells. This results in the production of IL-17 and IL-22, which may mediate the development of the epidermal hyperplasia and tissue inflammation observed in psoriasis.
There is therefore a need for improved means to follow the efficacy of treatment options against psoriasis, identify patients that will most benefit from these treatments in Psoriasis and other inflammatory diseases, and to determine and adjust the dosages of therapies for patients as may be needed.